Date: Mon, 7 Jul 2003 07:35:40 +1000 From: Peter Jeremy <peter.jeremy@alcatel.com.au> To: Chuck Swiger <cswiger@mac.com> Cc: freebsd-stable@freebsd.org Subject: Re: Weird vmstat -s stats Message-ID: <20030706213540.GU430@gsmx07.alcatel.com.au> In-Reply-To: <3F07576F.4030105@mac.com> References: <200307051728.24681.me@farid-hajji.de> <44brw8g26e.fsf@be-well.ilk.org> <200307060029.00866.me@farid-hajji.de> <3F07576F.4030105@mac.com>
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On 2003-Jul-05 18:55:43 -0400, Chuck Swiger <cswiger@mac.com> wrote: >Farid Hajji wrote: >[ ... ] >>Shouldn't such counters be at least 64 bit wide? > >You betcha. :-) The problem is that a 32-bit CPU, like the Intel x86 >family, can't increment a 64-bit counter atomicly. This isn't absolutely true. You _can_ perform atomic 64-bit operations on an x86 (for x>=5), they are just extremely expensive. There are regular threads on this sort of problem and I don't believe anyone has come up with a solution that did not involve overheads that were considered unacceptable in the general case. Peter
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